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BROWNS FERRY h0 CLEAR PLANT Verification Program on Wall Thickness of Valves Important to Nuclear Safety PREPARED BY :
J. S. Webb dj/[/4 Metallurgical eer/
Date J. M. Winebrenner O h4P_ M [d /[f/V MetallurgicalEnfeer
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SUBMITTED BY:
M. N. Bressi
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.A _ -
/(/U[
J j Pr' cipal Nuclear Engineer Date 7'I (C
4, Standard and Materials)
APPROVED:
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7 mom-7M
. PATTERSON Data Ch chanical Engineer TENNESSEE VALLEY AUTHORITY DIVISION OF ENGINEERING DESIGN MECHANICAL ENGINEERING BRANCH KNOXVILLE, TENNESSEE i
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1 Verification Program on Wall Thickness of Valves Important to Nuclear Safety TABLE OF CONTENTS i
Section Page No.
FOREWORD.
11 l
ACKNOWLEDGEMENTS.
. iii 1.0 SCOPE,
1
2.0 INTRODUCTION
2 i
3.0 TEST PROCRAM 3
3.1 MINIMUM WALL THICKNESS VERIFICATION 5
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3.2 MEASUREMENT METHODS 5
3.2.1 Direct Physical Method..
5 3.2.2 Ultrasonic Method 5
3.2.2.1 Evaluation of UT Equipment 5
3.3 PROCEDURE FOR MEASUREMENT 6
3.3.1 Calibration Blocks.
6 3.3.2 Probe Accuracy.
7 3.3.3 Calibration Records and Frequency 7
3.3.4 Calibration 7
3.4 VALVE WALL MEASUREMENT.
8 3.5 TEST PROCEDURE......
9 3.6 TRANSMISSION OF RESULTS 10 3.7 REVIEW OF RESULTS 10 4.0
SUMMARY
AND CONCLUSIONS.
11 5.0 REMAINING WORK
........................ 14 6.0 ATTACHMENTS AND APPENDICES 14 1
e FOREWORD In the course of.'nspections conducted by the Atomic Energy Commission's Directcrate of Regulatory Operations it was observed that a number of facilities had been supplied with valves whose wall thickness did not meet the minimum requirements specified by the applicable codes, standards, and procurement specifications.
Further investigation into this problem disclosed that licensees had I
not been able to document whether or not their valves met minimum wall thickness. This investigation also revealed that the minimum valve wall thickness problem could not be limited to any particular class of licensee nor to a specific valve supplier. Therefore on June 30, 1972, al) licensees of operating plants, plants under con-struction, as well as plants under design but not yet granted con-struction permits were notified by the Directorate of Regulatory Operations that verification of the wall thickness of valves important to nuclear safety would be required.
This report addresses itself to the approach taken by the Tennessee Valley Authority in meeting this requirement for the Browns Ferry Nuclear Plant.
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ACKNOWLEDGEMENTS The writers wish to thank Messrs. R. T. Hathcote, Project Manager, and M. M. Price, Construction Engineer at the Browns Ferry plant site for their support and cooperation in the performance of the field work required for this program, and to all supervisory personnel involved in this task.
Particular thanks and appreciation are due to Messrs. K. A.
Hastings and K. C. Nichols, Mechanical Engineering Associates, who were the Level II Ultrasonics Nondestructive Examination Technicians who performed the actual measurements.
l iii
1.0 SCOPE The program described in this report was formulated to provide a complete verification of the wall thickness of valves important to nuclear safety as required by the letter RO:II:JGD 50-259, 50-260, and 50-296 dated June 30, 1972.1 Although three of the plants docketed by TVA were recipients of this letter, only the Browns Ferry site was sufficiently advanced in the construction cycle to receive full and immediate attention, and is the subject of this report. Other plants will be handled separately.
2.0 INTRODUCTION
The problem of valve wall thinning has been known to the industry f,or many years. Castings, by their nature, are the most adaptable product form for the multi-curved, multi-chambered free-form bodies of valves. The basic advantage of weight savings and proper allocation of material carries with it the inherent disadvantage of possible improper wall thickness due to pattern misalignments and core shifts.
The Atomic Energy Commission's letter dated June 30, 1972, was the first time any requirement to document the wall thickness of valves important to nuclear safety had been required of industry.
TVA, having been a recipient of that letter, immediately began contacting valve manufacturers that had supplied valves for Browns Ferry Nuclear Plant to see if documentation could be obtained on 1
valve wall thickness.
1.
All pertinent correspondence is enclosed in Section A, Attachment I to this report and will henceforth be referenced only by sender and date of the letter.
2 The June 30, 1972, letter from AEC required TVA to notify the Commission within thirty (30) days of what records were available and when an AEC inspector could examine them. TVA responded to the June 30, 1972, letter on July 28, 1972, and informed the AEC that due to the required accumulation of information from several vendors that TVA would not be able to advise the AEC of action taken by TVA until September 15, 1972.
On July 17, 1972, TVA received letter BF-4507 from General Electric i
Company concerning minimum wall thickness documentation for reactor coolant pressure boundary valves. This letter pointed out that there I
were no Code or NSSS Contract requirements for recording of wall thicknesses for valves and that neither the Quality Assurance Program 1
outlined in Appendix D of the FSAR nor the detailed APED Quality I
Assurance Procedstres implemented in response to the Quality Assurance have required such documentation. GE also outlined in this letter APED's position and recommendations on the subject of minimum valve wall documentation.
TVA was informed by several vendors that it was normal practice of valve vendors quality control to check wall thickness measurements to verify that they conform to the drawings, but there had been no requirements for dccumentation. However, TVA was assured by these vendors that the valves did meet the requirements of ANSI B16.5 and MSS SP-66.
After several weeks of accumulating information from all valve manufacturers supplying cast and forged valves important to nuclear safety at Browns Ferry Nuclear Plant, a list was prepared tabulating
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these valves and whether or not documentation was available. On September 29, 1972, TVA wrote a letter to AEC transmitting the list f
of valves important to nuclear safety and the disposition of each valve. TVA at this time also informed the AEC that the records i
could be reviewed by their inspector at the site at any time after f
I October 31, 1972. TVA also informed the AEC that by October 31, 1972, i
i they would notify them of the plans and tentative schedules for the verification of the valves for which no records were available.
TVA proposed in the above letter to the AEC to limit their verifi-
[
cation program to cast valves only and to verify wall thicknesses i
of valves larger than two inches nominal pipe size in water lines and larger than four inches nominal pipe size in steam lines.
TVA informed the AEC by a letter dated October 31, 1972, that they were
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continuing to develop plans for verification of wall thickness of certain Browns Ferry valves and that TVA would notify AEC of the I
tentative schedule for their implementation.
f On December 1, 1972, TVA submit'ted to AEC a formal proposal for measuring minimum valve wall thickness utilizing TVA Specification 5.M.1.1(b) entitled " Specification for Thickness Measurement" which is a part of TVA General Construction Specification G-29.
The proposal also consisted of the limits specified by TVA in a letter dated September 29, 1972, to the AEC and added the condition that only valves in Unit 2 and Unit 3 would be measured because TVA felt that this would provide the level of confidence required to guarantee that all valves in the Browns Ferry Plant meet the standards and specifications under which they were purchased.
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4 On February 15, 1973, AEC, while not formally acknowledging nor rejecting either the September 29 or December 1, 1972 TVA proposals, informed TVA that all valves, both forged and cast, related to nuclear safety in Units 1, 2, and 3 must have wall thicknesses documented. Also, that this requirement applies to valves exceeding one and one-quarter (1 1/4) inches nominal pipe size in water lines and greater than two and one-half (2 1/2) inches nominal pipe size in steam lines.
Upon receipt of February 15, 1973 letter, TVA prepared to conduct a minimum wall thickness verification program in accordance with the guidelines defined in this AEC letter and the previously referenced AEC letter dated June 30, 1972. TVA procedure 5.M.l.l(b) was utilized in the program (it will be discussed later in the body of this report). Also, after the February 15, 1973 AEC letter, TVA construction personnel at Browns Ferry began utilizing the ultrasonic equipment purchased for the verification program i-to train personnel in operation and calibration of the equipment.
3.0 TEST PROGRAM The verification program developed by TVA to fulfill the requirements imposed by AEC in their letters to TVA dated June 30, 1972, and February 15, 1973, is contained in TVA procedure 5.M.1.l(b) entitled
" Specification for Thickness Measurement." This procedure is part of General Construction Specification G-29 and included in Section M, Attachment I to this report.
It describes the utilization of the direct physical method and the ultrasonic method for measuring wall thickness.
a 5
3.1 MINIMUM WALL THICKNESS VERIFICATION Many of the valves in this plant are ANSI B16.5 and the wall thickness required is tabulated in the standard. However, several of the valves are of non-standard design. For these valves TVA performed several spot checks of wall thickness calculations. These calculations are made part of this report and are listed in Section L of Attachment I.
3.2 MEASUREMENT METHODS 3.2.1 Direct Physical Method Physical measurements were accomplished by the use of micrometers, calipers, dial indicators and combinations of these measuring devices.
The above measuring devices were calibrated for accuracy against certified measurement standards which have a known valid relationship to national standards.
The actual calibration records for the measuring devices are included in Section B of Appendices I, II*,
and III* of this report. Also, the certification for the standard gauge blocks that relate back to the National Bureau of Standards are included in Section H Attachment I to this report.
I 3.2.2 Ultrasonic Method The ultrasonic measurement method for wall thicknesses described in TVA procedure 5.M.1.1(b) is accomplished by using the transmit-receive pulse-echo-method equipment which has an accuracy of measurement within 2 percent of the thicknesses being measured.
3.2.2.1 Evaluation of UT Equipment An evaluation of two popular ultrasonic thickness gauges were made by TVA site personnel on December 4, 1972, to determine l
- In course of preparation
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which gauge would be most adaptable to future thickness testing requirements at Browns Ferry Nuclear Plant. The evaluation consisted of a comparison of several measurements taken on dif-ferent types of material with a Nortec NDT-120 CSS and also with a Krautkramer D-Meter. The different types of materials on which the gauges were tested consisted of cast valve bodies, forgings, pipes, and plates which had already had micrometer readings taken on the thicknesses and recorded. The results of the gauge readings were recorded and compared to the actual micrometer readings. A copy of this comparison is included in Section B of Attachment I.
Due to these characteristics--accuracy, digital readout, compactness, and versatility--TVA site personnel found the Krautkramer D-Meter superior to the Nortec NDT-120 CSS and most acceptable for TVA future needs.
It was also decided by site personnel that, due to grain struc-ture and the thickness of valves to be tested, purchase of two optional probes should be made for use with the Krautkramer D-Meter. The two probes bought were the KHS-2 (2MHZ, 1" diameter) probe and a KMR-4 (4 MHZ, 1/2" diameter) probe.
Information concerning the Krautkramer D-Meter and the probes used can be found in Section C and D, j
Attachment I, to this report.
l 3.3 PROCEDURE FOR MEASUREMENT 3.3.1 Calibration Blocks TVA procedure 5.M.l.l(b) requires that equipment be calibrated on step wedge calibration blocks with a calibration step thickness within 0.1 inch of the thickness being measured. The calibration blocks are required by the procedure to be made from the some "P-Number" (as identified in ASME Code Section IX, table Q-ll.1) as the
7 material being measured. For the purpose of this program, P-Numbers 1, 3, 4, and 5 are considered equivalent. If material availability permitted, the calibration block material would be made from the same material type and product form as the material being measured.
3.3.2 Probe Accuracy The procedure further requires that each test probe used be tested for accuracy on curved surfaces by calibrating on the step wedge calibration blocks and then checking for reproduci-bility and accuracy on a curved surface which has a radius equal to or less than that of the item to be measured and of the same thickness as the step calibrated against on the step wedge for each probe.
3.3.3 Calibration Records and Frequency IVA procedure 5.M.l.l(6) requires that all details of the test equipment used, including test conditions be recorded for each test performed, that calibration of the equipment be performed at least once for each item or component, and calibrated again at least once for each thickness range.
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3.3.4 Calibration The TVA site personnel at Browns Ferry Nuclear Plant implenented TVA procedure 5.M.l.l(b) in the following manner as described in a TVA memorandum dated May 23, 1973. Material of the same P-Number as the valves to be measured was obtained from available vendors and shipped to Browns Ferry for machining into step wedge calibration
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8 blocks.
The receiving reports on the material for the calibration blocks can be found in Section E, Attachment I, of this report.
After the machining process, each step of each block was measured with micrometers (which were calibrated to standard gauge blocks) a minimum of three times, and the thickness was permanently stenciled on each step. Pictures and drawings of these calibration blocks are included in Section F and G of Attachment I.
To assure each block was comparable to the valves tested, a comparison test was made of each block against measurements of uninstalled valves.
At this time, both the KMS-2 and the KMR-4 probes were tested for accuracy and reproducibility on a curved surface with a radius equal to or less than the valves to be measured. Both probes were evaluated and found satisfactory for use in performing the valve thickness measurements.
It should be noted that both glycerine and Krautkramer paste, the couplants selected for use in the test, were compared on each step of each calibration block. The couplants were deemed comparable with a maximum deviation of.003" for material' thickness over 2.500".
3.4 VALVE WALL MEASUREMENT
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After verification of test equipment and calibration references, Browns Ferry NDE personnel, who were certified as Level II ultrasonic inspectors in accordance with SNT-TC-1A, performed the inspection of Unit 1 valves in accordance with TVA procedure 5.M.l.l(b).
A copy of the NDE certification of the Browns Ferry personnel performing I
the wall thickness measurements is included in Section A, Appendix I, of this report. All calibration data was performed in accordance l
with Browns Ferry Construction Procedure BF-57 and these records l
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9 are included in Section B, Appendix I.
All measurements taken were submitted to TVA DED for verification and acceptance. As a redundant measure to assure all required valves were checked, a detail study of TVA drawing 47W817-1, flow diagram (indluded in Section J.
Attachment I) was made, and all valves measured were properly marked on the drawing. Review of the complete systems shows that all required valves were measured.
3.5 TEST PROCEDURE The Browns Ferry NDE personnel measured valve wall thickness in accordance with IVA procedure 5.M.l.l(b) which consisted of at least two measurements taken in each octant of items being measured.
For valves, this requirement applied separately to the body, neck and weld or flange ends.
For purposes of orientation, O' was con-sidered top dead center when looking into runs of the items, or components, and, for branches, was the top of the plane including the axis in the direction of flow and the branch axis, with degree escalation clockwise. Prior to measurement, temporary markings were placed on the item or component near the point of measurement indicating location.
The minimum thickness for each octant was recorded and identified with the item, location and method of measurement. The results were recorded separately for each item on the appropriate form and are contained in Section C, Appendix I, of this report. The minimum thickness at weld ende was measured immediately adjacent to the weld preparation.
For valves larger than 4 inches nominal pipe size, sufficient measurements were made to assure that the wall thickness dimension
10 at weld ends did not reduce the body wall thickness to less than that required for minimum body wall thickness within a region closer to the outside surface of the neck than one minimum body wall thickness, tm, measured along the run direction.
3.6 TRANSMISSION OF RESULTS The thickness measurements made by the Browns Ferry NDE personnel on Unit 1 were completed May 1, 1973, and transmitted to DED the same day, as indicated by a TVA memorandum dated May 1, 1973.
It was pointed out in this memorandum that the measurements shown on the ultrasonic data sheets are ultrasonic measurements that need to be multiplied by the correction factor shown on each data sheet to obtain the actual wall thickness. On May 15, 1973, a TVA memorandum from TVA DED was sent to Browns Ferry Nuclear Plant stating that the data sheets documenting valve wall thickness obtained by NDE site personnel were acceptable and that all valves met design requirements.
It is pointed out at this point that DEC or Browns Ferry site personnel did not know what values for valve wall thickness were acceptable.
3.7 REVIEW OF RESULTS For purposes of standardization, TVA DED established acceptance standards for valve wall thickness by multiplying the calculated i
or catalog required wall thickness value by 1.02, which exceeded J
the worst calibration error but was within the limits permitted by the AEC June 30, 1972, letter. These values were then compared with the reported thicknesses.
On one safety valve, MPL-2-71, one measurement did not meet this requirement. However, DED referred to the actual calibration
11 error for that thickness and used that value for multiplying the required wall thickness to establish the acceptance standard.
It was determined that the wall thickness did meet design requirements, within the limits of measurement error for that material and thickness combination.
4.0
SUMMARY
AND CONCLUSIONS TVA measured the wall thickness of all valves in Class I safety systems 1 1/2 inch nominal pipe size and over in accordance with TVA Process Specification 5.M.l.1(b) " Specification for Thickness Measurements" dated September 6, 1972, with the exception of the valves manufactured by Darling Valve Manufacturing Company. These valve wall thickness dimensions had been previously measured by the vendor and valves with i
wall thickness less than specified on the design drawing were repaired.
The valves for which records were available are indicated in Section D, Appendix I, of this report.
TVA did not invoke the stated exception in their letters of September 29, 1972, and December 1, 1972, to AEC to measure the wall chickness of cast steel valves larger than 2 inch nominal pipe size in water lines and 4 inch nominal pipe size in steam lines. The valve list attached to the TVA September 29, 1972, letter to.AEC was extended to meet the requirements of the AEC letter of June 30, 1972, and included forged steel valves. This list is included in Section K of Attachment I.
Also, TVA did not invoke the statement made in their December 1, 1972, letter to AEC that the measurements of all Class I safety system valves in Units 2 and 3 would provide the level of confidence required to 1
guarantee that all Unit i valves met the standards and specifications under which they were purchased primarily because the AEC letter of
j 12 ib February 15 ignored the proposal, and time to fuel loading was becoming critical.
Instead, TVA measured all valves iS Unit 1 which had no documentation in accordance with AEC letter dated June 30, 1972.
The TVA valve wall thickness verification program for reactor coolant boundary valves meets the requirements of AEC letter dated February 15, 1973, which clarified the AEC position. The remainder of this report will discuss each item of the above letter and 2
reference the reasonse to the TVA verification program made by the AEC in a letter dated July 16, 1973, based on an inspection conducted by Mr. Kelley of the AEC on May 15-18 and 29, 1973, at the Browns Ferry site and the Knorvf.11e office. The July 16, 1973, AEC letter is included in Section A, Attachment I:
Item 1, " Valve Sizes," required that all valves, cast and forged, of sizes listed for BWR's in the June 30, 1972, AEC letter to i
licensees were to be included in the licensees' valve verification program, unless specific exceptions were permitted by Items 3, 4, 5.
TVA met this requirement by measuring all valves, cast and forged.
of sizes listed for BWR's in the June 30, 1972, AEC letter to licensees.
Item 2, " Acceptable Measurement Techniques and Accuracy," permitted any measurement to be used for acceptance purposes provided it could be shown to yield meaningful valve wall thickness measurements. A 2% maximum error in repeatability and accuracy was the original AEC goal and was met by TVA. TVA demonstrated this accuracy and
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repeatability by comparing physical measurements with ultrasonic
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t 13 measurements of calibration test blocks and comparing these values against physical and ultrasonic measurements of uninstalled valves.
Item 3, " Conditional Acceptance," Item 4, " Valve Verification Alternatives," and Item 5, " Valve Acceptance Through Evaluation or Special Testing" were not applicable to TVA's valve wall thickness verification program since all valves installed in Unit 1 that required documentation met minimum design valve wall thickness requirements.
One valve OKPL-2-71) out of eleven identical safety relief valves supplied by GE had an area that was questionable. The standard required wall thickness provided to TVA by GE for these valves was 1.875 inches. TVA (to assure the valves met the minimum wall thickness requirement) added the 2.0% instrument error tolerance permitted in AEC letter dated February 15, 1973, to the 1.875 inches, requiring a wall thickness of 1.91 inches. On the valve in question, one area measured 1.891 inches. TVA then used the actual established -
instrument error of 0.63% which'provides an acceptance standard thickness of 1.887 inches for this one valve. With this adjustment, the wall thickness of the valve was acceptable and therefore all valves measured by TVA exceed design minimum wall thickness requirements.
It is TVA's opinion that the valve wall verification program presented in this report meets all the requirements imposed on TVA by AEC in their June 30, 1972, letter.
v - - - - - - - - _ _ _ _
14 5.0 REMAINING WORK Work remaining to be done consists of the measurements of Units 2 and 3 valves which will be added to this report as Appendices II and III. At the suggestion of the AEC inspector, subsequent recording of measurements need only list the minimum reading for an area scan, but recorded at the proper angular position. This should go a long way in reducing the manhour requirements of this task.
6.0 ATTACHMENTS AND APPENDICES One attachment and three appendices are part of this report:
Appendices I, II, and III contain four sections labeled A through D with the following information:
A.
Certification of Nondestructive Examination Personnel B.
Calibration Records (BF-57 Attachments)
C.
TVA Valve Wall Thickness Measurement Records D.
Manufacturers' Wall Thickness Verification Records Attachment I to this report contains other essential information discussed in this report. It contains 12 sections as follows:
A.
Referenced Correspondence Filed Chronologically B.
Evaluation of Two Ultrasonic Thickness Gauges C.
Description and Price List of Krautkramer D-Meter and Optional Equipment D.
Conversion Table for Krautkramer D-Meter E.
Receiving Report of Material for Calibration Blocks F.
Pictures of Calibration Blocks i
G.
Drawings of Calibration Blocks H.
Certification of Standard Gauge Blocks J.
TVA Drawing 47W817-1. Flow Diagram
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1 15 4
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BFNP Units 1-3 Valve Wall Thickness Tabulation 1
1 L.
Spot Check Calculations 4
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M.
TVA Specification 5.M.1.1(b), " Specification for Thickness Measurement" i
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6 BROWNS FERRY NUCLEAR PIANT VERIFICATION PROGRAM ON WALL THICKNESS OF VALVES ATTACHMENT I REFERENCED INFORMATION UNITS 1, 2 AND 3 TABLE OF CONTENTS l
SECTION SUBJECT A.
Referenced Correspondence Filed Chronologically B.
Evaluation of Two Ultrasonic Thickness Gauges i
C.
Description and Price List of Krautkramer D-Meter i
and Optional Equipment i
D.
Conversion Table for Krautkramer D-Meter i
E.
Receiving Report of Material for Calibration Blocks F.
Pictures of Calibration Blocks 1
G.
Drawings of Calibration Blocks H.
Certification of Standard Gauge Blocks.
i J.
TVA Drawing 47U817-1, Flow Diagram
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BFNP Units 1-3 Valve Wall Thickness Tabulation i
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Spot Check Calculations M.
TVA Specificatica 5.M.l.l(B) " Specification for Thickness Measurement" l'b;,!!:,;f,;a a
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DIRECTO.uTE OF REOULATORY OPERATIONS In Reply Refer To:
June 30, 1972 RECrlVED JUL 1 0 1072; T,G:II:JGD MECHAt lCAL DM'Gt!
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- ,0-259, 50-260 mwr - ace i --
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~~ ~ ~ T l-~~ ~ 12 Tennessec Valley Authority i
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Mr. J. E. Uatson
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93s Manager of Power
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Gentleman:
~I This letter relates to your reactors Brouns Ferry 1, 2, and 3 and v s Sequoyah I cnd 2.
Information obtcined during inspections conducted by the Directorate of v
n2;ulatory Operations, hcs disclor.ed that a nu.ber of fccilitics have been ~
ec,uipped with valves with wall thicknesens belcu the ninh.ec requirca:nts specified by the applicable codes, standards and procurement specifiention.s.
In other instcnces, licensees have not been cble to docu.ncat uhethc.: or not tnair valves cat ninicus ucli thickness requirer. ants. Our survey 'cf this subject has disclosed ' hat the catter is not linited to any class.of t
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licensee or valve supplier.
In light of the chove infpruction, you crc requested to verify, thro 49 canufccturing records or/other suitchle c:ans, that valves irportant tc j
ncclear scfety instclied or to be instclled at your facilitics cact the ninitura vall thickness recuirec. ants of the specified codes or stcndards.
'20 the extent that verification records are currently availchle', you are requas:ed to pronatly accumulate those records at the plant site, and to advise this of fice withir. thirty (20) days of the date of this-letter, of
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uhat recard:, are availabic and when our inspector may examine them at rS ' /
plcat site.
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SUGGEST
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i Tenacsscc Valley Authority June 30, 1972 in the event t. hat records are not currently availnble, you are requested to advise this office uithin thirty (30) days, of your plans and schedules for s!ctonstrcting by suitable citerncte neans, that valves icportant to nuclear safety installed or 'co be installed. at your fccilitics arc ccecptable uith respect tc.us11 thickness.
Records of conforcance shall be acintained current with inspections performad.
The valves uhich require demonstrntion of acceptchle uall thickness are the follouing.
Each valyc within.the reactor coolant pressure' boundary, as defined in subsection 50.55(4 (Codes and Standards) of 10 CFR 50,t/nere the valve is:
(a) over 1-inch nominal pipe size for pressurized water reactors; (b) over 1 1/4-inch noninal pipe cice in unter lines for boilin3 uater reactors;
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(c) ovar 21/2-inch nominal pipa siac in steam lines for boilin3 j
uater reactors.
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Th2 folicwing techniq cs are consiGered to be a suf ficient demonstration cf acccatchle vall thickness.< 'Alterncte techniques cay be offered, but chare is na assurance that they vill be found acceptcbic:
' (1) Documented direct physical necsuremant of cetual vall
~~ ' thickness, with comparison to specified tiniaun wall
^
thickness.
(2) Documented results of ultrasonic reasurement of uall thickness, uith compcrison to specified ninicum wall thickness, and documentation that the ulcrcsonic measura-cant technique is demonstrated to hava a nexinun error
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in repeatchility and accuracy, of not nore thcn 2% of the vall" thickness.
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(3), Wcll thichnasses, verified by either of the sove techniques, to be not less than 90% of spacified
-*-icum uall thichness vill be acceptcble, provided that the documented cachanical characteristics of the narerial exceed the specific: tion ninitum by an a=ount sufficient to co=pensate for tha =casured reduction in uc11 thickness, (4) "Speci,fied Minimua Unll Thickacss" as used chove, means the vall thickness required by the relevant codes and sc ndards (e.g., ASA B31.1 (1955) ; USAS 331.1.0 (1957) ;
USAS B16.5; liSS-S?-66) in ef fect on the date of the purcha::e order.
(5) Certain of your valvas may hava, for procurcaant convenience, been ordered to ratings higher than actually required by service conditions.
In such instances, you may, if you uish, provida for our review, an engineering justification for accepting valves uhich do not conform to procure: cat specifi-cations, but do, in your opinica, satisfy sc.rvice requirenents. Such justification should be promptly trcasaitted to this office, in ten (10) ccpies.
(6) In certain instances, you rey wish to repair velvas found to have vall thickness belcu the specified nininua.
In such instances you cra rec.uestad to provide to this offica for our review, the proposed repair procedura, includin; a description of technicues to be used to verify the acceptability of the repaired co ponents.
Such a proposed procedure should also be submitted in tan (10) copics.
i.cceptable docunentation of conformance with the abova requirements nu t be completed within three (3) years of the date of this letter.
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Very truly yours, D
A, usfr i 6< % ~
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/JohnC. Davis 7-10-72--DRP:ER b Dir CC CC:
L. D. Weber, W3 UB-K,
D. R. Patterson M. N. Bressler - Coordinate our reply. We vill reply through Weber.
J. C. Eberacle' v
J.'I. Givens R. M. Pierce B. S. Montganery C.A.Chandley(3)-Pleasesendcopicst,oGEimmediately. We must reach agreement with then on Browna Ferry on valve wall thicknesses.
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